Transfer dies are widely used in the stamping industry to perform various metal forming operations on sheet metal. More specifically, a metal component to be formed is inserted into a transfer die between a lower die assembly and an upper die assembly. Prior to the stamping operation, the stamping or part to be formed is located on a support plate which is operably coupled to a lifter unit. During the stamping operation, the upper die assembly is lowered onto the lower die assembly such that the part is stamped therebetween. The downward movement of the upper die assembly causes the support plate to move downwardly, thereby enabling the part to engage the lower die assembly. After the stamping operation is completed, the upper die assembly moves upwardly away from the lower die assembly and the part is raised to a position between the upper and lower die assemblies on the support plate.
Prior art transfer dies included a lifter unit having two distinct components, namely a lift pin cylinder supported on the lower die assembly for reciprocal movement and operably coupled to a transfer plate at an end opposite the support plate, and a spring assembly disposed between the lower die assembly and the transfer plate for biasing the lift pin cylinder away from the upper die assembly. Due to the positioning of these components, access to both the top and the bottom of the transfer die is required for installation and maintenance of the lifter unit. In addition, the transfer plate occupied additional space which creates the potential for interference during the operation of the transfer die. Moreover, each lifter unit had to be specifically designed for a particular transfer die due to variations in the dimensions of the lower die assembly.